In many medical treatment and operative procedures it is necessary to hold a patient's head in a particular position. For instance a patient's head is held in a fixed predetermined position while a fracture or dislocation of the cervical spine is healing, as by utilizing a conventional halo traction device, or during neurosurgery, utilizing an operating table head holder. While the patient's head is being immobilized, however, it may also be desirable to subject the patient's skull to an imaging procedure, such as a CT scan, digital subtraction angiography, sonography, magnetic resonance imaging, computer enhanced flat film X-raying, and the like. Therefore it is highly desirable that the affixation apparatus be made of a material which does not artifact significantly (e.g. any more than bone does).
According to a first aspect of the present invention, a skull pin is provided which does not artifact any more than bone does. The skull pin may be used with a conventional halo, with an operating table head holder, or with other skull fixation apparatus used in medical treatment or operative procedures. Typically skull pins are made out of stainless steel and are a total block to CT or magnetic resonance imaging of the skull. This greatly limits the physician in the types of apparatus that may be utilized for head immobilization for a number of medical operative procedures. For instance accident victims may have brain swelling caused by impact, which can result in inter-cranial pressure and resulting death or brain damage. Imaging of the brain, as with a CT scanner, is a desirable way to check for brain swelling. If the accident victim has a broken neck, or the like, the physician will not utilize a halo or tongs to stabilize the broken neck (even though they are highly desirable for that purpose) because the physician cannot then monitor brain swelling utilizing imaging because of the blockade resulting from stainless steel skull pins, or the material of the halo or tongs itself.
According to the present invention, a skull pin is provided which allows effective imaging of a patient's skull, yet provides the desired skull fixation in an effective manner. The skull pin according to the invention includes a skull engaging portion which terminates in a pointed tip, and is of ceramic. Most desirably the skull engaging portion is of a single crystal ceramic material, such as single crystal alumina ceramic commercially sold under the trademark "BIOCERAM" by Kyocera International, Inc. of West Los Angeles, Calif. This material does not artifact any more than does bone; however it has a brittleness that does not allow the skull pin to be made wholly of it. Therefore the skull pin according to the invention also comprises an exteriorly threaded elongated cylinder of plastic, having first and second ends. Preferably the plastic is a carbon fiber reinforced plastic, or boron fiber reinforced plastic, such as shown in U.S. Pat. Nos. 4,055,862 and 4,146,793. The skull engaging portion is fixed to the plastic cylinder, as by an integral shaft of the skull engaging portion extending into an opening within the cylinder and adhering to the cylinder along the entire area thereof. The cylinder also has a screwdriver blade-receiving slot, or other structure to allow driving of the skull pin, at the second end thereof.
According to the present invention, there also is provided a generally ring-shaped member for skull immobilization that not only does not interfere with imaging but also provides fixation in a very secure manner. This generally ring-shaped member, which may be referred to as a "crown", can take the place of halos for most procedures in which halos are now utilized. It is rigid and has a plurality of threaded openings therein for receipt of skull pins. It preferably is of carbon fiber or boron fiber reinforced plastic, and has a shape and dimensions so as to maintain rigidity during use. A first, major portion thereof is in a first plane, and a second portion thereof slants out of the first plane. During use in a medical treatment or operative procedure, the second, out of plane portion extends downwardly to a position below the "equator" of the patient's head, that is to a position below a capital-distal plane extending between the top of the patient's ears and the top of his eyes. The crown is affixed to the patient's head by skull pins passing through openings in the second portion of the crown. Preferably the crown also has a generally horseshoe shape in plan view, with first and second ends spaced from each other, the first and second ends comprising part of the second portion of the crown. Such a shape facilitates utilization of the crown.
It is the primary object of the present invention to provide for affixation of a patient's head, in an effective manner, during a medical treatment or operative procedure in such a way so that imaging of the patient may be practiced without unacceptable blocking. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.